伊犁河谷汛期一次短时强降水雨滴谱特征分析

Characteristics of the Raindrop Spectrum during a Short-time Strong Precipitation Episode in the Yili River Valley

利用常规地面、高空、新一代天气雷达以及雨滴谱资料,对2012年8月3日发生在伊犁河谷一次较大范围暴雨的天气形势、雷达回波特征和降雨微物理特征等进行深入分析。200 h Pa西风急流、500 h Pa中亚低涡和地面冷锋是这次强降雨过程的天气背景。通过对暴雨雨滴谱演变分析得出,对流性降水是这次暴雨的主要组成部分,对流云团微物理结构存在明显的不均一性,存在多个强降水中心,水平尺度多维持在10 km左右,持续时间短,降水集中且雨滴浓度大,雨滴谱宽及分布差异大。同时分析雨滴谱演变特征、降水微结构特征、以及各种特征参量(平均直径Da、最大直径Dmax、粒子浓度N,雨强R,雷达反射率因子DBZ)、分雨强雨滴谱特征和ZR关系等。通过对这些量的分析,初步了解到了伊犁河谷短时强降水微物理结构特征。

Using conventional ground and aerial data, new generation of weather radar data, raindrop size distribution data, the background, characteristics of radar echo and microphysical characteristics of a rainstorm occurred in wide range of Yili river valley on August 3, 2012 were analyzed. The results showed that 200 hPa West Siberia westerly trough , 500 hPa Central Asia vortex and surface cold front were the main impact of the heavy rainfall system. The bell shape of the valley terrain resulting in airflow mechanical compression, and triggering convection, terrain forcing air uplift had important influences on the enhanced convection and precipitation. This precipitation process was laminated hybrid cloud precipitation, where large areas of strati-form clouds embedded in multiple convective clouds, these clouds were connected together to constitute the convective rain bands. The storm caused mainly by the convective clouds of which the microphysical structure was obvious in heterogeneity and there were multiple centers of heavy precipitation, the horizontal scale mainly maintained around 10 km, duration mainly from five minutes to 10 minutes. The raindrops had high concentrations, generally above 1,000 m^-1. The raindrop size distribution width was wide and very different. The high concentrations of particles less than 1 mm occupied 60% of all sizes, but their contribution to rainfall intensity accounted for about 20%.